Abstract:

 To investigate the characteristics, diffusion pattern, and grouting filling effect of synchronous cementsodium silicate grout in superlargediameter shield tunnels, an insitu experiment of synchronous doublecomponent grouting is performed in the negative ring section of the shield tunnel project of the BeijingHarbin expresswayLuyuan north street section on Beijing East Sixth Ring road. The shield tail grouting gap is formed by installing a steel sleeve on the section, and earth and pore water pressure sensors are employed to monitor the pressure distribution and variation in the shield tail gap, and the gelling characteristics and preliminary diffusion pattern of the doublecomponent grout are obtained. After the completion of synchronous grouting, the mechanical properties and filling effect of the doublecomponent grout are analyzed and tested by onsite sampling and threedimensional laser scanning. The test results reveal the following: (1) The sensor as a whole changes in a "single peak" curve, i.e., when the grouting starts, the sensor value increases sharply, the sensor value drops suddenly after the grouting stops, and finally, the sensor value drops slowly and stabilizes at a certain value. (2) Owing to the large temperature change and low humidity outside, as well as uneven mixing and unstable product of the doublecomponent grout, the compressive strength obtained by sampling at the test site is slightly lower than that measured in an indoor test. (3) The threedimensional laser scanning results show that the synchronous doublecomponent grout can fill the shield tail gap well after appropriate parameter improvements and that the grouting circle has no obvious defects.

Key words:

super-large-diameter shield tunnel, synchronous double-component grouting, in-situ test, grout diffusion form, grout filling effect